It is increasingly common for automotive vehicles to be equipped with traction control systems. Such systems are designed to control the speed of a driven wheel to a desired level in order to improve vehicle stability, particularly on driving surfaces having low coefficients of friction.
More specifically, an imbalance between engine torque and road torque acting on a vehicle wheel can cause the wheel speed to exceed the desired level, which is typically referred to as wheel spin. To control such wheel spin, traction control systems generally employ engine or brake management to control the engine torque acting on the wheel.
In automatic transmission vehicles, while operating in a traction control mode, shifting of the automatic transmission powertrain can also contribute to such torque imbalances. Indeed, such shifting can cause sudden and significant disturbances in driven wheel speeds. In turn, such shift-created wheel speed transients can momentarily reduce vehicle stability.
As a result, there is a need for an improved traction control method and system that reduces driven wheel speed transients related to transmission shifting during a traction control event. Such a method and system would reduce such transients using coordinated engine and transmission control.